Recent studies have revealed that the urinary bladder (UB) epithelium (urothelium) is involved in sensory mechanisms and can release chemical mediators (nitric oxide; ATP). Localization of afferent nerves next to the urothelium suggests these cells may be targets for transmitters released from bladder nerves or that chemicals released by urothelial cells may alter afferent excitability. Both afferent nerves and urothelial cells exhibit common properties including the expression of certain receptors and channels. For example, demonstration of vanilloid receptors (VR1) in urothelial cells sensitive to capsaicin and protons suggests that VRI in non-neuronal cells may have a role in sensory mechanisms. Moreover, the properties of afferents and urothelial cells are plastic and can be changed by pathology. Our data suggest that altered production of mediators following injury/inflammation may influence afferent excitability and urothelial function, by increasing permeability to noxious substances. This suggests that the epithelium is involved in intercellular signaling and that neural-epithelial interactions can play a critical role in the regulation of afferent excitability. Using a multidisciplinary approach involving molecular biology, transmitter release, imaging techniques using photodiode arrays and in vivo monitoring of afferent and reflex bladder activity, our goals are to further characterize the properties of urothelial cells and determine the signaling mechanisms responsible for cell-cell (neural-epithelial, inter-epithelial) interactions. Aim #1 will evaluate the intracellular signaling mechanisms underlying the neuron-like properties of urothelial cells. Although urothelial cells and sensory neurons exhibit common properties, little is known about mechanisms involved in urothelial signaling and how they might influence bladder function. This aim will examine the mechanisms involved in chemo-and mechanical signaling in urothelium. Aim #2 will evaluate the chemical mechanisms involved in cell-cell signaling. This aim will explore the transmitter/signaling mechanisms involved in neural-epithelial interactions and the impact on signaling in the urothelium. Aim #3 will evaluate the effect of pathology on urothelial properties/signaling. This aim will examine the impact of inflammation and injury on signaling pathways in urothelial cells and on communication with other cell types. Elucidation of mechanisms impacting on urothelial function may provide insights into the pathology of bladder dysfunction.